Can't answer all of that, but might be able to help some.
There are folks here that do glass cutting. There's a place that was on.. Riverside I think that did cuts for reasonable pricing. Had some cut for a non-fishtank related project a few years back. I'll see if I can dig up their name.
Live food and plants can both be found at D&G Pets. The plants are basically good quality, especially if you get them soon after they get them in.
No idea on the betta hobbyists or CO2. I've heard Jax will do CO2 refills, but I'm not positive on that. I'd be willing to bet there's somewhere that will do it for a reasonable price, though.